Method for putting on standby and method for reactivating at least part of a wireless communication network and gathering node of said network

ABSTRACT

A method for reactivating a wireless communication network in accordance with one of the IEEE 802.11 standards is described. The communication network comprises a plurality of gathering nodes, each gathering node comprising at least one access-point and/or user radio-frequency interface and/or a user of a so-called backhaul wireless network associated with the communication network, which are deactivated in sending mode, 
     A beacon frame sent by a master node of the reactivation method is propagated gradually in order to reactivate all the nodes in the network.

TECHNICAL FIELD

At least one embodiment relates to the field of wireless communicationnetworks in accordance with one of the IEEE (Institute of Electrical andElectronics Engineers) 802.11 standards, that is to say those wirelesscommunication networks commonly referred to as Wi-Fi networks. At leastone embodiment relates more particularly to a method for putting onstandby and a method for reactivating at least part of such a network.

PRIOR ART

A wireless communication network (hereinafter “network”) in accordancewith one of the IEEE 802.11 standards typically comprises a plurality ofnodes. Each node is an electronic device comprising at a minimum aradio-frequency module for establishing communications in accordancewith one of the IEEE 802.11 standards, or in other words in accordancewith one of the Wi-Fi standards. Such a network typically comprises anelectronic device, commonly referred to as an access point or AP, and aplurality of so-called user (or client) electronic devices able toestablish wireless connections with the access point and/or with eachother. In a residential environment, the electronic device access pointis typically a box supplied by an internet operator, that is to say ahome gateway or residential gateway. User electronic devices aretypically computers, televisions, tablets or so-called smartphones. Itis thus commonly said that user electronic devices are associated “inWi-Fi” with the access point. The architecture of a Wi-Fi network mayalso be distributed, in order for example to extend the range of thenetwork or to increase the performances thereof, through the use of aplurality of access points. The architecture of a distributed Wi-Finetwork is different from the previous architecture briefly described. Adistributed Wi-Fi network comprises at a minimum two networks:

-   -   a so-called gathering or infrastructure (backhaul) network,        making it possible to connect the access points to each other        and to form a network infrastructure in accordance with a        network architecture of the mixed star and/or chain type, this        backhaul network may be a wireless network (for example Wi-Fi),        a cable network (for example Ethernet) or a mixture of the two,    -   a so-called user (or client) Wi-Fi network (fronthaul) allowing        a connection of so-called user (or client) nodes (or electronic        devices) to the distributed Wi-Fi network.

In the backhaul network, a parent-child hierarchy is created between twoconnected Wi-Fi devices. One of the Wi-Fi devices becomes the parent ofthe other Wi-Fi device, the other Wi-Fi device becoming a child of theparent Wi-Fi device. The parent Wi-Fi device fulfils a role of accesspoint for the child Wi-Fi device. The child Wi-Fi device fulfils a roleof station for the parent Wi-Fi device.

FIG. 1 illustrates highly schematically such a distributed Wi-Fi network100. The distributed network 100 comprises a gateway 110 and a pluralityof nodes or electronic devices B1 101, B2 102, B3 103, B4 104, C1 105and C2 106. The gateway 110 allows an interconnection of the network 100with a network 120, for example the internet. In this example, the nodesB1, B2, B3 and B4 are so-called gathering nodes. These nodes B1, B2, B3and B4 constitute the backhaul infrastructure of the network 100. Thenodes C1 and C2 are two user nodes connected to gathering nodes(respectively the nodes B3 and B4). The gathering nodes B1, B2, B3 andB4 manage two Wi-Fi networks:

-   -   a first Wi-Fi network, dedicated to gathering, allows an        association of each gathering node with the distributed network        100, possibly in a meshed fashion,    -   a second Wi-Fi network is dedicated to the association of the        user nodes, in a similar fashion to a non-distributed Wi-Fi        network.

Thus each node B1, B2, B3 and B4 of the infrastructure comprises aplurality of radio interfaces:

-   -   a radio interface known as “AP-B” (standing for “access point        backhaul”) corresponding to a point-of-access interface of the        Wi-Fi network dedicated to gathering,    -   a radio interface known as “ST-B” (standing for “station        backhaul”) corresponding to a user (or client) interface of the        Wi-Fi network dedicated to gathering,    -   an “AP-F” radio interface (standing for “access point        fronthaul”) corresponding to an access-point interface of the        Wi-Fi network dedicated to the association of user nodes of the        distributed network 100.

In the example illustrated in FIG. 1, the node B1 101 is connected bycable to the gateway GW 110, for example via an Ethernet connection.According to one embodiment, the connection between the gateway GW 110and the node B1 101 may be made by a Wi-Fi connection. According to acomplementary embodiment, the gateway GW 110 and the node B1 101 are oneand the same electronic device, said electronic device comprising thefunctionalities of the gateway GW 110 and of the node B1 101.

Each gathering node B1, B2, B3 or B4 can therefore possibly establish aconnection to another gathering node in order to constitute the backhaulinfrastructure of the distributing network 100. More precisely, agathering node may, via the “ST-B” radio interface thereof, establish aconnection to an “AP-B” radio interface of another gathering node inorder to form a gathering-node chain. Some gathering nodes may beconnected via a cable connection, for example of the Ethernet type.

An AP-B radio interface, an access point of the Wi-Fi network dedicatedto gathering, establishes a Wi-Fi network associated with a networkidentifier SSID (service set identifier) corresponding to the backhaulnetwork. A gathering node must therefore know this SSID in order toestablish a Wi-Fi connection to another gathering node. A gathering nodeis adapted for retransmitting the traffic (that is to say the data,exchanged in messages) received via its access point fronthaul “AP-F”and access point backhaul “AP-B” radio interfaces to its stationbackhaul “ST-B” radio interface in order to transfer the trafficreceived to a central node of the distributed network, here the node B1101. Likewise, a gathering node is adapted for redistributing thetraffic received via its station backhaul “ST-B” radio interface to oneor other or both of its access point fronthaul “AP-F” and/or accesspoint backhaul “AP-B” radio interfaces. In other words, in the exampleillustrated in FIG. 1, the gathering node B3 103 is adapted for:

-   -   receiving traffic gathered by the node B4 101 via its radio        interface AP-B,    -   receiving traffic from connected user nodes, for example the        user nodes C1 105, via its AP-F interface,    -   retransmitting said traffic received to the gathering node B1        101 via its station backhaul ST-B radio interface, and    -   conversely, redirecting traffic received via its station        backhaul ST-B radio interface to the node B4 104 via its AP-B        interface and/or the gathering node B1 101 via its station        backhaul ST-B radio interface.

The nodes of the backhaul network thus communicate with each other bymeans of logic links, for example IP communications or encrypted tunnelsor communications in accordance with a proprietary communicationprotocol.

Such a network broadcasts numerous electromagnetic signals and is also ahigh consumer of energy. Consequently putting all or part of the networkon standby is known. Being able to reactivate the network or the networkpart put on standby is also known.

Thus the patent application US 2010/0195551 describes a method forputting on standby a mesh wireless communication network wherein amaster node sends directly, or through relays, to slave nodes, aninstruction to go on standby (or sleep instruction). This method isassociated with the implementation in each slave node of an intermittentreception function making it possible to receive a reactivation (orreawakening) instruction coming directly or indirectly from the masternode. However, the methods described are not compatible with the CSMA-CAprotocol used by the 802.11 standards. This is because this protocoldoes not make it possible to know the actual instants of sending of theframes. Moreover, the methods described do not make it possible to putthe network on standby or reactivate it from just any node in thenetwork. It is therefore necessary to propose methods for overcomingthese drawbacks.

DISCLOSURE OF THE INVENTION

According to a particular embodiment, a method for reactivating awireless communication network in accordance with one of the IEEE 802.11standards is described. The network comprises a plurality of gatheringnodes organised in a parent/child hierarchy, at least one gathering nodein said communication network, referred to as the current node,comprising an access-point and/or user radio-frequency interface of aso-called backhaul wireless network associated with the communicationnetwork that are deactivated in sending mode. The method is executed bysaid current node and comprises;

-   -   receiving a first beacon frame comprising state information        indicating a reactivation; and

a) putting in memory state information on said current node in order toindicate that a reactivation is under way;

b) reactivating all the backhaul radio-frequency interfaces of saidcurrent node;

c) broadcasting a second beacon frame comprising state informationindicating a reactivation;

d) pairing with a parent node and, in the case where said current nodehas child nodes, waiting until said child nodes pair with it andchecking that said child nodes are reactivated; updating an internalstate indicating that said current node is reactivated. According to aparticular embodiment, the current node further comprising anaccess-point radio-frequency interface of a wireless network known as afronthaul network associated with the communication network that isdeactivated in sending mode and in reception mode, the method comprises,after the step b), a step of reactivating said access-pointradio-frequency interface of said fronthaul network in sending mode andin reception mode.

According to a particular embodiment, said first beacon frame furthercomprises timestamp information corresponding to the time at which saidreactivation was triggered, said steps a) to d) being performed solelyin the case where a value of said timestamp information received ishigher than a value of current timestamp information associated withsaid current node.

According to a particular embodiment, the step a) further comprises theputting in memory of the timestamp information received in place of thevalue of the current timestamp information.

According to a particular embodiment, said second beacon frame furthercomprises the timestamp information received.

According to a particular embodiment, said first beacon frame furthercomprising a key identifying said network, said steps a) to d) areperformed solely in the case where said key identifying said network ofsaid beacon frame is identical to an identification key stored in memoryof said current node.

According to a particular embodiment, said reactivation is triggered bypressing on a button of said master node.

According to a particular embodiment, said network being reactivated,the method comprises, for a node of said network referred to as areceiving node:

1) Receiving a message from a node in the network, referred to as arequesting node, comprising a standby request; and

if said receiving node is a node not having any adjacent node other thansaid requesting node:

2) Sending a message to said requesting node indicating that it acceptsthe standby request;

3) Receiving a message comprising a standby instruction;

4) Sending a message to said requesting node acknowledging the standbyinstruction;

5) Going on standby while storing in memory connection information anddeactivating in sending mode its access-point and/or userradio-frequency interfaces of said backhaul network;

otherwise:

-   -   Sending a message to said requesting node indicating that it        refuses the standby request and an indication that it is an        intermediate node;    -   Repeating the steps 1) to 5) recursively for each of the nodes        adjacent to said receiving node distinct from said requesting        node with said receiving node acting as a new requesting node,        until all the nodes adjacent to said receiving node are put on        standby;    -   Sending a message to said requesting node comprising a request        for enabling standby;    -   Receiving a message comprising a standby instruction;    -   Sending a message to said requesting node acknowledging the        standby instruction;    -   Going on standby while storing in memory connection information        and deactivating in sending mode its access-point and/or user        radio-frequency interfaces of said backhaul network.

According to a particular embodiment, going on standby further comprisesdeactivating its access-point radio-frequency interface of the fronthaulnetwork in sending mode and in reception mode.

According to a particular embodiment, the message comprising the standbyrequest comprises information indicating that it is a standby requestand an identifier of the requesting node.

According to a particular embodiment, the message comprising the standbyrequest further comprises an identification key particular to saidnetwork.

According to a particular embodiment, the message comprising the standbyinstruction comprises information indicating that it is a standbyinstruction and an identifier of the node sending the message.

According to a particular embodiment, the message comprising the standbyinstruction further comprises a time value defining an instant at whichsaid receiving node must go on standby.

According to a particular embodiment, the message comprising the standbyinstruction further comprises the identification key particular to saidnetwork of said standby request.

According to a particular embodiment, the message comprising the standbyinstruction further comprises an identifier of a channel on which theradio interfaces of said receiving node must reactivate themselves.

According to a particular embodiment, the message comprising thestandby-enabling request comprises information indicating that it is astandby-enabling request and an identifier of said node sending saidmessage.

According to a particular embodiment, a gathering node of a wirelesscommunication network in accordance with one of the IEEE 802.11standards is described. The gathering node comprises an access-pointand/or user radio-frequency interface of a so-called backhaul wirelessnetwork associated with the communication network which are deactivatedin sending mode. The gathering node is configured to execute the stepsof the method described above according to any one of the embodiments.According to a particular embodiment, a computer program is described.The computer program comprises instructions for implementing, by aprocessor of a gathering node of a distributed wireless communicationnetwork comprising a plurality of gathering nodes, the method describedpreviously according to any one of the embodiments, when the computerprogram is executed by the processor. According to a particularembodiment, a recording medium is described. The recording medium can beread by a management node of a distributed wireless communicationnetwork, on which the computer program described above is stored.

BRIEF DESCRIPTION OF THE DRAWINGS

The features mentioned above, as well as others, will emerge moreclearly from a reading of the following description of an exampleembodiment, said description being made in relation to the accompanyingdrawings, among which:

FIG. 1 illustrates schematically the architecture of a distributedwireless communication network comprising a plurality of nodes, forexample in accordance with an IEEE 802.11 standard;

FIG. 2 illustrates schematically a method for putting on standby adistributed wireless communication network in accordance with one of theIEEE 802.11 standards according to a particular embodiment;

FIG. 3 shows a node A requesting and nodes B, C and D receiving astandby request;

FIG. 4 illustrates schematically a method for putting on standby adistributed wireless communication network in accordance with one of theIEEE 802.11 standards according to another particular embodiment;

FIG. 5 shows a node A requesting and nodes B, C and D receiving astandby request, said node B being an intermediate node;

FIG. 6 illustrates schematically a method for reactivating a distributedwireless communication network in accordance with one of the IEEE 802.11standards according to a particular embodiment;

FIG. 7 illustrates schematically a method for reactivating a distributedwireless communication network in accordance with one of the IEEE 802.11standards according to another particular embodiment; and

FIG. 8 illustrates schematically the hardware architecture of agathering node of a distributed wireless communication network, thegathering node being adapted for executing all or some of the steps ofthe methods illustrated in FIG. 2, FIG. 4, FIG. 6 or in FIG. 7.

DETAILED DISCLOSURE OF EMBODIMENTS

At least one embodiment makes it possible to put on standby adistributed wireless communication network in accordance with one of theIEEE 802.11 standards or a part of such a network. This putting onstandby being able to be triggered, e.g. by a user, from any node in thenetwork.

At least one embodiment makes it possible to reactivate a distributedwireless communication network in accordance with one of the IEEE 802.11standards (or respectively a part of such a network) which haspreviously been put on standby. This reactivation being able to betriggered, e.g. by a user, from any node in the network. FIGS. 2 and 4illustrate schematically a method for putting on standby a distributedwireless communication network in accordance with one of the IEEE 802.11standards, for example the network 100, or a part of this network. Inthe remainder of the document, a node is considered to be a “requestingnode” if it makes a standby request to another node. A node isconsidered to be a “receiving node” if it receives a standby requestcoming from a requesting node.

In FIGS. 2 and 4, the steps performed in a requesting node areidentified by the letter S and the steps performed in a receiving nodeare identified by the letter E. FIG. 2 illustrates more particularly thestandby method in the case where the node receiving the standby requestis a node not having adjacent nodes other than the requesting node. Thisis the case with the nodes B, C or D in FIG. 3. In this figure, the nodeA is the requesting node. The method is described with the node A as therequesting node and the node B as the receiving node. In the case of aplurality of adjacent nodes, the method described is implemented witheach of the nodes adjacent to the requesting node, in this case thenodes B, C and D in FIG. 3.

During the standby method, the requesting node A stores in memoryinformation representing the state of the standby method in relation tothe receiving node among the following states:

-   -   Ready: default state, the node is switched on and ready to        interact in the case of the standby method;    -   Interrogated: the standby request has been sent, the receiving        node has therefore been interrogated and the requesting node is        awaiting a response;    -   Accepted: the standby request has been accepted by the receiving        node;    -   Refused: the standby request has been refused by the receiving        node;    -   Awaiting: the receiving node must send a response to the        requesting node;    -   Cancelled: the standby procedure is cancelled; and    -   On standby: the receiving node is on standby.

During a step S200, the requesting node A of the wireless communicationnetwork detects a triggering by a user of a putting of the network onstandby. The requesting node A may be any node in the wirelesscommunication network. The triggering of the standby may be done by auser by pressing on a physical button of the requesting node A.According to a variant, the triggering of the standby is performed by auser via a user interface attached to the requesting node. Therequesting node will then start the standby method.

During a step S210, the requesting node sends in unicast mode, to anadjacent node B, then considered to be a receiving node, a message M1comprising a standby request. It also changes the state of the standbymethod in relation to the receiving node into “interrogated”. Theadjacent nodes are the nodes in the backhaul network adjacent to therequesting node, i.e. accessible from the requesting node in a singlehop. The message is for example transmitted by means of a communicationbus through a cable link or a wireless link (e.g. Wi-Fi or Bluetooth).

The message M1 comprises:

-   -   information for defining the message category (here a standby        request). This information may be a numerical identifier for        defining the category of the message among a set of message        categories;    -   an identifier of the node A sending the message (identifying in        the topology e.g. its MAC address);    -   optionally, a key identifying the network making it possible to        identify the latter. This key is for example generated randomly        by the node that initiated the putting of the network on        standby, i.e. the node from which the standby was triggered.        This makes it possible to immunise the network against pirate        reactivation. Optionally the key could serve to encrypt the        messages exchanged; and    -   optionally, a list of the identifiers of the nodes through which        the request passed. This list makes it possible to know the        topology of the network from the node originating the initial        standby request. This is because the putting on standby        propagates recursively from a node originating the initial        request to ends of branches. During a step E200, the receiving        node B receives the message M1 comprising the request to put the        network on standby. On receiving the standby request, the        receiving node B can accept or refuse the request and where        applicable indicate the reason for refusal. In FIG. 2, the        receiving node B accepts the standby request.

In a step E210, the receiving node B therefore sends a message M2 to therequesting node A identified in the message M1, said message indicatingthat the receiving node accepts the standby request. The message M2comprises:

-   -   Information for defining the message category (here response to        a standby request). This information may be a numerical        identifier for defining the category of the message among a set        of message categories;    -   An identifier of the node B sending the message (identifying in        the topology e.g. its MAC address);    -   A response to the message M1: acceptance of the standby request;        and    -   Optionally, a list of its adjacent nodes. This information        enables the node A to have a view of the nodes adjacent to the        node B. This information makes it possible in particular to        complete the topological view of the system and to give to the        node A a preview of propagation downstream through the knowledge        of the nodes adjacent to the node B.

In a step S220, the requesting node A receives the response, i.e. themessage M2, sent by the receiving node B. In the case of a plurality ofadjacent nodes, messages are received by all its adjacent nodes. Onreceiving a response (message M2) and if the request is accepted, therequesting node A will change the state of the method associated withthe receiving node into “accepted” and will send a standby instruction.The request having been accepted, the requesting node A, in a step S230,sends to the receiving node B a message M3 comprising a standbyinstruction.

The message M3 comprises:

-   -   Information for defining the message category (here standby        instruction). This information may be a numerical identifier for        defining the category of the message among a set of message        categories;    -   An identifier of the node sending the message (identifier in the        topology, MAC address);    -   Optionally a time value for defining the instant when the nodes        must go on standby. If the value is zero then the standby is        immediate. If this value is not present in the message M3, it is        supposed to have a value defined by default, e.g. a zero value;    -   Optionally, information identifying a so-called “reactivation”        channel that will be used by all the nodes in order to detect        therein an activity leading to a reactivation/reawakening of the        system. This channel may be the current channel used before        putting on standby or be different. However, if the current        channel is a DFS channel, the node initiating the standby        request must choose a non-DFS channel. It may select the least        busy channel before putting on standby or take a default        channel;    -   Optionally, the key identifying the network defined in the        message M1 if such is present; and    -   Optionally, the list of identifiers of the nodes through which        the request passed.

During a step E220, the receiving node B receives the message M3comprising the standby instruction and in return sends a messageacknowledging the standby instruction.

In a step E230, the receiving node B goes on standby.

If the time value defined in the message M3 comprising the standbyinstruction is equal to zero, the node goes on standby immediately.Otherwise it does so in a deferred manner. Thus, if the time valuedefined in M3 is a period, the node goes on standby after the periodindicated in M3 has elapsed. When the receiving node B goes on standby,it performs the following actions:

-   -   It saves the connection information (BSSID, SSID, password) in        order to be able to subsequently reconnect to the network and to        keep the same topology as before the standby. Optionally, it        saves the key identifying the network and data for identifying        the channel, e.g. a channel number identifying a frequency band,        used before the standby. The latter information will for example        be able to be used during arbitrations by a management node,        following a reactivation of the system on the reactivation        channel, in order to switch all the nodes in the backhaul        network onto a more appropriate channel; and    -   It deactivates its AP-B and ST-B radio interfaces solely in        sending mode, these remaining active in reception mode. The        deactivation of the AP-B and ST-B radio interfaces allows        deactivation of the AP-F radio interfaces in sending mode and in        reception mode. This is because, as soon as the AP-B and ST-B        radio interfaces are deactivated, no more information is        exchanged through the AP-F radio interfaces. In a variant, the        AP-F radio interfaces are left active. This variant makes it        possible to detect an activity of a mobile terminal, e.g. a        telephone that is switched on again, and to trigger a        reactivation of the system from this detection. Optionally,        before or after the putting on standby, it also configures the        channel by applying the one, i.e. the “reactivation” channel,        that is indicated in the message M3 comprising the standby        instruction. Thus the receiving node B will listen out on this        reactivation channel in order to detect thereon any reactivation        instructions.

In a step S240, the requesting node receives the acknowledgementmessage. This acknowledgement enables the requesting node, i.e. the onethat sent the standby instruction, to go on standby in its turn. In thecase of a plurality of adjacent nodes, as illustrated in FIG. 3, therequesting node goes on standby when it has received the acknowledgementmessages from all the receiving nodes B, C and D. Optionally, therequesting node, if it is capable of operating on the same frequenciesas the receiving node B, analyses its radio environment in order tocheck that the receiving node has indeed stopped transmitting and hastherefore gone on standby. The requesting node A can then change thestate of the method associated with the receiving node “on standby”.

FIG. 4 illustrates the standby method wherein the node B receiving thestandby request is an intermediate node, i.e. a node that is notsituated at the end of a chain and which therefore itself has adjacentnodes C and D other than the requesting node, as illustrated in FIG. 5.In this figure, A is the requesting node. The node A sends a standbyrequest to the node B. In this case, the node B will refuse the standbyrequest since it is a node intermediate between the node A and the nodesC and D. The node B will then in its turn initiate a standby request toits own adjacent nodes (C and D) in accordance with the method describedabove with reference to FIG. 2.

In a step S200, the requesting node A of the wireless communicationnetwork detects a triggering of a putting of the network on standby,e.g. by a user. The requesting node A may be any node in the wirelesscommunication network. The triggering of the standby may be done by auser by pressing on a physical button of the requesting node. Accordingto a variant, the triggering of the standby is performed by a user via auser interface attached to the requesting node. The requesting node willthen start the standby method. In a step S210, the requesting nodesends, in unicast mode, to an adjacent node, in this case the node B inFIG. 5, a message M1 comprising a standby request. It also changes thestate of the standby method in relation to the receiving node B into“interrogated” mode. In the case of a plurality of adjacent nodes, themessage M1 is sent to all its adjacent nodes. The message is for exampletransmitted by means of a communication bus through a cable link or awireless link (e.g. Wi-Fi or Bluetooth).

In a step E200, the receiving node B receive the message M1 comprisingthe request to put the network on standby.

In a step E215, the receiving node B sends a message M2 to therequesting node A, said message M2 indicating that it refuses thestandby request. The message M2 comprises:

-   -   Information for defining the message category (here response to        a standby request). This information may be a numerical        identifier for defining the category of the message among a set        of message categories;    -   A response to the message M1: refused;    -   A reason for the refusal: intermediate node; and    -   Optionally, the list of its adjacent nodes.

This is because the node B, being an intermediate node, must firstensure that all its adjacent nodes are on standby before accepting astandby request.

In a step S225, the requesting node A receives the response sent by thereceiving node B. If the request is refused, the reason for the refusalis analysed. In the case where the reason is “intermediate node”, therequesting node will then change the state of the method in relation tothe receiving node into “on standby”.

In a step E216, the intermediate receiving node triggers the standbymethod for its adjacent nodes apart from the requesting node, in thiscase for the nodes C and D in FIG. 5. The steps in FIG. 4 are thereforeimplemented with the node B as the requesting node and the node C or Das the receiving node. In this case, in the step S200, the triggering ofthe standby for the node B is detected not by a user but by thereception of the message M1 comprising the standby request coming fromthe node A. The steps of the standby method are therefore appliedrecursively.

In a step E218, once the nodes C and D are on standby, the intermediatereceiving node B sends to the requesting node A a message M4 comprisinga request to enable standby.

The message M4 comprises:

-   -   Information for defining the category of message (here a request        to enable standby). This information may be a numerical        identifier for defining the message category among a set of        message categories; and    -   An identifier of the node B sending the message (identifier in        the topology, e.g. its MAC address).

In a step S228, requesting node A receives the message M4 comprising therequest for enabling standby.

In a step S230, the requesting node sends a message M3 comprising astandby instruction. It changes the state associated with the node Binto “accepted”.

In a step E220, the receiving node receives the message M3 comprisingthe standby instruction and goes on standby.

In a step E230, the receiving node B sends a message acknowledging thestandby instruction.

In a step S240, the requesting node receives the acknowledgementmessage. This acknowledgement enables the requesting node, i.e. the onethat sent the standby instruction, to go on standby in its turn. In thecase of a plurality of adjacent nodes, as illustrated in FIG. 3, therequesting node goes on standby when it has received the acknowledgementmessages from all the receiving nodes B, C and D. Optionally, therequesting node, if it is capable of operating on the same frequenciesas the receiving node B, analyses its radio environment in order tocheck that the receiving node has indeed stopped transmitting and hastherefore gone on standby. The requesting node A can then change thestate of the method associated with the receiving node into “onstandby”.

Naturally, if one of the nodes C or D itself has adjacent nodes, themethod described in relation to FIG. 4 is applied with the node C or Das the requesting node and its adjacent nodes as receiving nodes. Thus,gradually, the whole of the wireless communication network is put onstandby.

In a particular embodiment (not shown in FIGS. 2 and 4), the standbyrequest may be refused by a receiving node for type of reason other thanbeing “intermediate node”. In a variant, a receiving node may notrespond to a standby request since it is not joinable, for examplebecause it is switched off or disturbed. In all these cases (i.e.refusal for a type of reason other than being “intermediate node” orabsence of response), the requesting node will change in memory thestate of the standby method relating to the receiving node into“refused”. This is because a receiving node may be non-joinable. Becauseof this, it cannot be informed of the putting of the network on standby.In this particular case, the standby procedure is cancelled. Therequesting node informs the other nodes of the stoppage of the standbyprocedure. Where applicable, it may request the nodes already put onstandby to reactivate, e.g. by using the method described with referenceto FIGS. 6 and 7. The nodes that have received the request to cancel thestandby have their states configured to “cancelled” at the requestingnode. The nodes that are not yet put on standby receive a cancellationrequest and apply the same procedure recursively. The cancellationrequest must be acknowledged. On reception of the acknowledgement, therequesting node changes its state and configures it to “ready”.

In a particular embodiment, beacon frames may be broadcast in order toinform all the nodes in the wireless communication network that thelatter is in the process of being put on standby. More precisely, thenode from which the standby was triggered adds, in at least one beaconframe, information (IE) indicating that the network is in the process ofbeing put on standby. In a variant, this node adds, in at least onebeacon frame, information (IE) indicating the state of the standbymethod, i.e. whether it is under way, terminated, cancelled, etc.

The method according to at least one embodiment advantageously makes itpossible to put at least part of the network on standby and therefore tosave on energy and to limit the unnecessary broadcasting ofelectromagnetic signals. Moreover, this standby can be triggered fromany node in the network.

FIGS. 6 and 7 illustrate schematically a method for reactivating adistributed wireless communication network in accordance with one of theIEEE 802.11 standards, for example the network 100, said wirelesscommunication network comprising a plurality of gathering nodes, some ofwhich at least are on standby. The nodes have been able to be put onstandby via the method described with reference to FIGS. 2 and 4 or byany other method allowing a standby resulting in a deactivation of the“AP-B” and “ST-B” backhaul radio interfaces solely in sending mode,these remaining active in reception mode. In a variant, the deactivationof the “AP-B” and “ST-B” backhaul radio interfaces in sending mode wasfollowed by a deactivation of the “AP-F” radio interfaces in sendingmode and in reception mode. The connection information (e.g. basicservice set identifier, SSID and password), optionally theidentification key and the channel used before the standby will alsohave been saved in memory during the standby procedure. Moreparticularly, FIG. 6 illustrates the method from the point of view of aso-called master node, from which the method for reactivating thenetwork is triggered, and FIG. 7 illustrates the method from the pointof view of another node in the network.

With reference to FIG. 6, in a step S600, a node in the wirelesscommunication network determines that a reactivation of the wirelesscommunication network has been triggered by a user. This node may be anynode in the wireless communication network. The reactivation may betriggered by a user by pressing on a physical button of the node.According to a variant, the reactivation is triggered by a user via auser interface attached to the node. The node will then start thereactivation method and becomes the master node of the reactivationmethod.

In a step S610, the master node puts in memory the information useful tothe reactivation of the network. In particular it stores in memory: itsinternal state that it configures to “reactivation” and timestampinformation so that it is equal to the time of the triggering by theuser of the reactivation. The internal state of the node gives anindication on the phase in which it is situated in the reactivationmethod. The “reactivation” state indicates that it is in the process ofreactivation and the “ready” state indicates that it is reactivated andthat it can therefore receive and transmit data via its radio interfacesin the same way as before the standby.

In a step S620, the master node reactivates all its radio interfaces. Inparticular, it reactivates its “AP-F” radio interfaces in sending modeand in reception mode and its “AP-B” and “ST-B” backhaul radiointerfaces in sending mode. In a variant embodiment, the master nodereactivates only its “AP-B” and “ST-B” backhaul radio interfaces insending mode. In this variant, its “AP-F” radio interfaces arereactivated in sending mode and in reception mode later, e.g. at the endof the step S650. The reactivation channel is used optionally during thereactivation of the system. If, during the reactivation, thereactivation channel is in service, it will continue to be used duringthe use of the network. This channel may be different from the channelused prior to the standby. In a variant embodiment, the master node, inS620, configures the channel used by its backhaul radio interfaces onthe channel defined before standby. In a step S630, the master nodebroadcasts, to all the nodes in the network, a message indicating tothem to reactivate. This is because the “AP-B” and “ST-B” radiointerfaces of the nodes are active in reception mode during the periodof standby of the network. Thus the nodes within range of the masternode remain configured to receive and read the messages broadcast by themaster node.

For this purpose, the master node adds, in its beacon frames,information IE (“information element”) comprising in particular theinformation useful to the reactivation of the network put in memory atthe step S610, i.e. its internal state configured to “reactivation” andoptionally timestamp information corresponding to the time of triggeringby the user of the reactivation. The IE optionally comprises anidentifier of the master node, e.g. its MAC address, and anidentification key negotiated before the network was put on standby inorder to identify the master node as indeed belonging to the network.The identification key may also be used as a hash key in order toencrypt these data in order to ward off any attacks.

In a step S640, the master node pairs with the node that was its“parent” before the standby. It checks that all its child nodes arepaired with it and that the state of all the nodes in the network isconfigured at “ready”. If such is the case, then the master node can inits turn configure as “ready” in a step S650. The “master” node is thelast node going to the “ready” state, which indicates that thereactivation method is terminated and that the network is functioning inthe same way as before the standby.

In a variant, the master node sends a message over the whole of thenetwork that must be acknowledged in cascade in the same way as for thestandby request in order to check that all the nodes are indeedreactivated. For example, with reference to FIG. 5, supposing that A isthe master node, it then sends to B a verification message, and Btransmits the message to C and to D. Once C and D have responded to B, Bresponds to A in order to confirm that its child nodes are reactivated.

With reference to FIG. 7, in a step S700, a node in the wirelesscommunication network, referred to as the current node, determines thata reactivation of the wireless communication network has been triggered.For a current node different from the master node, the step S700 (whichcorresponds to the step S600 for the master node) comprises the stepsS705 to S730.

In a step S705, the current node receives a beacon frame sent by themaster node or relayed by another node in the network.

In an optional step S710, the current node compares the timestampinformation Ts_received received in the beacon frame with its owntimestamp information Ts_current in order to check whether it is indeeda new event. If Ts_received is higher than Ts_current, the current nodechecks the state indicated in the IE of the beacon frame received. Inthe contrary case, it will consider that the beacon frame comprisesobsolete information and will ignore the beacon frame in a step S720.

If the state in the IE indicates “reactivation”, the current nodechecks, in an optional step S730, whether the identification keynegotiated before the standby and stored in its memory is identical tothe key indicated in the beacon frame received. If such is the case, itwill relay the reactivation information (state, timestamp information,identification of the master node, optionally identification key) to theother nodes. For this purpose, in a step S740, the current node puts inmemory the information useful to the reactivation of the network. Thisis done using the IE of the beacon frame received. In particular, itstores in memory its internal state by configuring it at “reactivation”.Optionally, it stores the value of Ts_received, which replaces the valueTs_current, and other data such as the identifier of the master nodeindicated in the IE. In a step S750, the current node reactivates allits radio interfaces. In particular, it reactivates its “AP-F” radiointerfaces in sending mode and in reception mode and its “AP-B” and“ST-B” backhaul radio interfaces in sending mode. In a variant, thecurrent node reactivates only its “AP-B” and “ST-B” backhaul radiointerfaces in sending mode. In this variant, its “AP-F” radio interfacesare reactivated in sending mode and in reception mode later, e.g. at theend of the step S780. The reactivation channel is used optionally at thetime of reactivation of the system. If, at the time of reactivation, thereactivation channel is in service, it will continue to be used duringthe use of the network. In a variant, it configures the channel used byits backhaul radio interfaces on the channel defined before standby.

In a step S760, the current node broadcasts the beacon frames comprisinginformation IE (“information element”) with the information useful tothe reactivation of the network put in memory at the step S740, i.e. itsinternal state configured at “reactivation”, the timestamp informationcorresponding to the time of the triggering by the user of thereactivation and the identifier of the master node. The IE optionallycomprises the identification key negotiated before the network was puton standby in order to identify the current node as indeed belonging tothe network. Thus, gradually, the information appearing in the beaconframe of the master node is relayed by other nodes in the network. In avariant, the current node adds its own identifier, e.g. its MAC address,in the IE. Thus it is possible to know through which nodes thereactivation information passed.

In a step S770, having knowledge of its close topology, the current nodewill pair with the node that was its “parent” before the standby. Thisis because the node, like any Wi-Fi equipment, has knowledge of andtherefore has in memory, independently of its operating state, the listof the stations (child nodes) that are associated on its AP-B interfaceand the access point (parent node) on which its ST-B interface isassociated.

If the current node did not have any child nodes before it was put onstandby, after pairing with its parent node it configures its internalstate to “ready” and updates its own timestamp information in order toindicate therein the time of its change of state in a step S780.

If the current node had child nodes before it was put on standby, itwaits until all its child nodes are paired with it. Optionally, itchecks by means of a scanning of its radio environment that theirinternal state is indeed configured at “ready”. If such is the case,then the current node, after pairing with its parent node, in its turnconfigures its internal state at “ready” and updates its own timestampinformation in order to indicate therein the time of its change of statein the step S780. Thus it in this way indicates that the reactivationmethod is completed for its branch.

In the particular case of a topology in a loop, the nodes havingknowledge of the topology change their internal state to “ready” onceall their “child” nodes have paired and are themselves associated withtheir “parent” nodes. All the nodes then periodically scan their radioenvironment in order to check whether each beacon frame sent by thenodes in the network does indeed contain the “ready” state. Once onlythe “ready” state is broadcast, the reactivation method is terminated.This approach can also be used in the context of a star topology and abranch topology.

The methods for putting on standby and reactivating the distributedwireless communication network can be implemented independently. Thusthe wireless communication network put on standby by the methoddescribed with reference to the steps in FIGS. 2 to 5 can be reactivatedby the method described with reference to FIGS. 6 and 7 or by adifferent method. In the same way, the wireless communication networkreactivated by the method described with reference to FIGS. 6 and 7 mayhave been put on standby previously by the method described withreference to FIGS. 2 to 5 or by a different method.

FIG. 8 illustrates schematically the hardware architecture of anelectronic device or gathering node 800 of a wireless communicationnetwork, the electronic device or gathering node being configured toperform all or some of the steps of the method illustrated in FIG. 2, inFIG. 4, in FIG. 6 or in FIG. 7. Thus the electronic device 800comprises, connected by a communication bus: a processor or CPU (centralprocessing unit) 801; a memory MEM 802 of the RAM (random accessmemory), ROM (read only memory) and/or EPROM (erasable programmable readonly memory) type, possibly a network module NET 803, for example of theEthernet type, a storage module STCK 804 of the internal storage typeand possibly a plurality of radio-frequency modules 805 to 80N inaccordance with a standard of the IEEE 802.11 type. The gathering node800 may optionally comprise one or more input/output interfaces, notshown in FIG. 8 (e.g. a keypad, a mouse, a touch pad) a webcam, etc.,each being configured to display information and/or to enable a user toenter commands or data. The gathering node 800 may also comprise anenergy source, not shown in FIG. 8, which may also be external to thegathering node.

The storage module STCK 804 may be of the hard disk drive (HDD) or SSD(solid-state drive) type or of the type consisting of an externalstorage medium reader, such as an SD (Secure Digital) card reader.

The processor CPU 801 can record data, or information, in the memory MEM802 or in the storage module STCK 804. The processor CPU 801 can readdata recorded in the memory MEM 802 or in the storage module STCK 804.These data may correspond to configuration parameters. The networkmodule NET 503, if present, typically enables the electronic device 800to be connected to a local network and/or the internet. Eachradio-frequency module 805 to 80N enables the electronic device 800 toestablish a plurality of radio-frequency interfaces in accordance with aso-called Wi-Fi standard. A radio-frequency interface may be a Wi-Fiaccess point, or on the other hand a so-called user radio-frequencyinterface enabling another electronic device to be associated with aso-called access-point radio-frequency interface. The processor CPU 801is capable of executing instructions loaded in the memory MEM 802, forexample from the storage module STCK 804. When the electronic device 800is powered up, the processor CPU 801 is capable of reading instructionsfrom the memory MEM 802 and executing them. These instructions form acomputer program causing the implementation, by the processor CPU 801,of all or some of the methods and steps described above, particularlythe method described in FIGS. 2 and 4 or the method described in FIGS. 6and 7. Thus all or some of the methods and steps described above can beimplemented in software form by the execution of a set of instructionsby a programmable machine, such as a DSP (digital signal processor) or amicrocontroller. All or some of the methods and steps described here canalso be implemented in hardware form by a machine or a dedicatedcomponent, such as an FPGA (field-programmable gate array) or an ASIC(application-specific integrated circuit). The functions of theelectronic device 800 may be integrated in a node of a wireless networkin accordance with an IEEE 802.11 standard by an updating of software,that is to say for example by an updating of the microprogram (firmware)of the electronic device 800.

1. A method for reactivating a wireless communication network inaccordance with one of the IEEE 802.11 standards comprising a pluralityof gathering nodes organised in a parent/child hierarchy, at least onegathering node in said communication network, referred to as the currentnode, comprising an access-point radio-frequency interface and a userradio-frequency interface of a so-called backhaul wireless networkassociated with the communication network, said access-point and userradio-frequency interfaces of said backhaul network being deactivated insending mode, the method being executed by said current node andcomprising: receiving a first beacon frame comprising state informationindicating a reactivation; and a) putting in memory state information onsaid current node in order to indicate that a reactivation is under way;b) reactivating, for said current node, all of its access-point and userradio-frequency interfaces of the backhaul network; c) broadcasting asecond beacon frame comprising state information indicating areactivation; d) pairing with a parent node and, in the case where saidcurrent node has child nodes, waiting until said child nodes pair withit and checking that said child nodes are reactivated; updating aninternal state indicating that said current node is reactivated.
 2. Themethod according to claim 1, wherein, said current node furthercomprising an access-point radio-frequency interface of a so-calledfronthaul wireless network associated with the communication networkthat is deactivated in sending mode and in reception mode, step b)further comprises a step of reactivating said access-pointradio-frequency interface of said fronthaul network in sending mode andin reception mode.
 3. The method according to claim 1, wherein saidfirst beacon frame further comprises timestamp information correspondingto the time at which said reactivation was triggered, said steps a) tod) being performed solely in the case where a value of said timestampinformation received is higher than a value of current timestampinformation associated with said current node.
 4. The method accordingto claim 3, wherein the step a) further comprises the putting in memoryof the timestamp information received in place of the value of thecurrent timestamp information.
 5. The method according to claim 3,wherein said second beacon frame further comprises the timestampinformation received.
 6. The method according to claim 1, wherein, saidfirst beacon frame further comprising a key identifying said network,said steps a) to d) are performed solely in the case where said keyidentifying said network of said beacon frame is identical to anidentification key stored in memory of said current node.
 7. The methodaccording to claim 1, wherein said reactivation is triggered by pressingon a button of a node of said wireless communication network.
 8. Themethod according to claim 1, wherein the method comprises, for a node ofsaid network referred to as a receiving node: 1) receiving a messagefrom a node in the network, referred to as a requesting node, comprisinga standby request; and if said receiving node is a node not having anyadjacent node other than said requesting node, a node being adjacent toanother node if it is accessible from this other node in a single hop:2) sending a message to said requesting node indicating that it acceptsthe standby request; 3) receiving a message comprising a standbyinstruction; 4) sending a message to said requesting node acknowledgingthe standby instruction; 5) going on standby while storing in memoryconnection information and deactivating in sending mode its access-pointand/or user radio-frequency interfaces of said backhaul network;otherwise: sending a message to said requesting node indicating that itrefuses the standby request and an indication that it is an intermediatenode; repeating the steps 1) to 5) recursively for each of the nodesadjacent to said receiving node distinct from said requesting node withsaid receiving node acting as a new requesting node, until all the nodesadjacent to said receiving node are put on standby; sending a message tosaid requesting node comprising a request for enabling standby;receiving a message comprising a standby instruction; sending a messageto said requesting node acknowledging the standby instruction; going onstandby while storing in memory connection information and deactivatingin sending mode its access-point and/or user radio-frequency interfacesof said backhaul network.
 9. The method according to claim 8, whereingoing on standby further comprises deactivating its access-pointradio-frequency interface of the fronthaul network in sending mode andin reception mode.
 10. The method according to claim 8, wherein themessage comprising the standby request comprises information indicatingthat it is a standby request and an identifier of the requesting node.11. The method according to claim 10, wherein the message comprising thestandby request further comprises an identification key particular tosaid network.
 12. The method according to claim 8, wherein the messagecomprising the standby instruction comprises information indicating thatit is a standby instruction and an identifier of the node sending themessage.
 13. The method according to claim 12, wherein the messagecomprising the standby instruction further comprises a time valuedefining an instant at which said receiving node must go on standby. 14.The method according to claim 12, wherein the message comprising thestandby instruction further comprises the identification key particularto said network of said standby request.
 15. The method according toclaim 12, wherein the message comprising the standby instruction furthercomprises an identifier of a channel on which the radio interfaces ofsaid receiving node must reactivate themselves.
 16. The method accordingto claim 8, wherein the message comprising the standby-enabling requestcomprises information indicating that it is a standby-enabling requestand an identifier of said node sending said message.
 17. A gatheringnode of a wireless communication network in accordance with one of theIEEE 802.11 standards, said network comprising a plurality of gatheringnodes organised in a parent/child hierarchy, said gathering nodecomprising an access-point and/or user radio-frequency interface of aso-called backhaul wireless network associated with the communicationnetwork which are deactivated in sending mode, said gathering node beingconfigured for performing the steps of the method according to claim 1.18. (canceled)
 19. A non-transitory storing a computer programcomprising instructions for implementing the method according to claim 1when said program is executed by at least one processor of a gatheringnode.